True or False?
Catalina Island was formed long ago by an ancient volcano.
Volcanoes form some islands, however Catalina Island was formed by geologic activity that pushed the Earth’s mantle to the surface forming the island. Once that super heated rock was pushed up, it was cooled by the ocean water, which formed Catalina Island as well as the other Channel Islands. This type of geologic movement is called subduction, specifically between two of the Earth’s tectonic plates. About 200,000 million years ago, the Farallon plate, sitting under the Oceanic Plate, began to subduct, or go under the North American Plate. This movement scraped up rock and sediment from the bottom of the ocean bringing it to the surface, forming what we know today as The Channel Island chain. This type of plate subduction took about 100 million years to break the surface, and to become the islands that we walk and roam present day.
Because of this type of subduction formation, Catalina Island is made up of three different types of rock; Igneous, Metamorphic, and Sedimentary which require heat, pressure, and sediment in order to form. The most primary rock composition of the island is made up of a type of metamorphic rock called blue and green schist, located mainly on the western and central parts of the island. Catalina is also made up of quartz, located on the east end of the island and in the middle canyon.
All of this rock talk can be lumped into a big category known as geology, or the study of rocks and how they change over time. I know, sounds kind of boring, but geology actually allows us to look into the past and understand our timeline as well as Earth’s history and place within the cosmos as we know it. Think of geology as Earth’s well-kept diary, shedding light on the secrets of land and ocean formation on our big blue planet.